Digital maps are found in a wide variety of devices, including car navigation systems, hand-held GPS units, mobile phones, and in many websites such as GOOGLE MAPS and MAPQUEST. Although digital maps are easy to use from an end-user's perspective, creating a digital map is a difficult and time-consuming process. Every digital map begins with a set of raw data corresponding to millions of objects such as streets, intersections, parks, and bodies of water. The raw map data is derived from a variety of sources, such as the New York City Open Accessible Space Information System (OASIS) or the U.S. Census Bureau Topologically Integrated Geographic Encoding and Referencing system (TIGER). In many cases, data from different sources is inaccurate and out of date. Oftentimes the data from the different sources are in a format that is not suitable for use in a real map. Integrating data from these heterogeneous sources so that it can be used and displayed properly is an enormous challenge.
In particular, the borders of objects in the raw map data may run roughly parallel, but not exactly parallel, to the borders of other objects. For example, the border of an object that represent a park may be jagged, which prevents the park from being accurately aligned with the roads that surround the park, which may have straight borders. When borders of adjacent objects are not accurately aligned, a thin open area appears between objects when displayed on a map, resulting in sub-optimal map rendering quality.